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I have a bare 69 IRS pan, and I need to order the rear suspension. It appears that the 1969 IRS cars came with a 26_9/16" length bar. I was wondering if I could use the shorter 21_3/4"? I would prefer the shortest option, to eliminate any potential issues with adjusting the spring plate with the body installed. 

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Thanks. @-Jonny B- I did see that one...  I guess the thing it didn't clarify, was if there was a difference in the housing lengths, and why the different years used different lengths. I know that there is a difference in spring plates, between the swing and IRS pans. My thoughts were to run the Shorter (swing axle spec torsion) with the IRS Swing plates. And what the reasoning, as to why they offer three different lengths to begin with..

@dlearl476 posted:

That’s a question for someone at SwayAway but afaik, there are 3 different lengths for three different torsion tubes: early swing, late swing, IRS.

All the torsion housings are the same length.  The torsion bars come in 3 lengths, as do the spring plates.  

You can use short torsion bars with the corresponding spring plates. Remember, the shorter the bar the higher the spring rate, given the same diameter.

@Eric N- use short (21 3/4?) early to mid '60's swingaxle torsion bars, take some corresponding spring plates, cut them to fit, drill some holes and use the swingaxle caps- do it right and they will bolt to stock irs trailing arms.  The torsion bars save close to a pound apiece over their longer irs counterparts, the spring plates are significantly lighter and the caps are lighter as well.  I drilled a few holes in the spring plates and iIrc saved about 5 lbs (in total).  I'll dig up pics and see if I can find the weight saving data later.  Al

Last edited by ALB

Weights- a stock 2 plate irs spring plate weighs over 2500 grams, while the (later?) 1 plate unit weighs some 1700 g (and change).  A Sway a Way irs spring plate (to be used with swingaxle torsion bars) weighs about the same as the the heavier stock irs spring plate. My cut down swingaxle spring plates (for irs trailing arms and the shorter torsion bars, which weigh about a pound less each than the irs bars) weighed 996 and 997 g, for a total savings of over 5½ pounds (and I never got around to weighing the stock irs end caps, which are significantly heavier than the swingaxle pieces- I'm going to have to find out!).

And I promised you a pic-                                                                                                                lightened spring plate- cut down for irs    This is what my spring plates look like.  Al

PS- the nice part about modifying and using the swingaxle  spring plates is stock suspension grommets will work and you don't have the clunky, squeaky red plastic crap in your car.

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  • lightened spring plate- cut down for irs
Last edited by ALB

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